Use of atracurium in cardiac surgery involving cardiopulmonary bypass with induced hypothermia.

Atracurium was administered by infusion to 12 anaesthetized patients undergoing cardiac surgery with cardiopulmonary bypass and induced hypothermia. Following an initial bolus dose of 0.6 mg kg-1, an infusion of atracurium was continued at an average rate of 0.0066 +/- 0.0003 mg kg-1 min-1 (0.4 mg kg-1 h-1) which was sufficient to maintain 90-95% block of the single twitch or train-of-four responses before bypass. Adequate surgical relaxation was provided with approximately half the rate of infusion of 0.0034 +/- 0.0003 mg kg-1 min-1 (0.2 mg kg-1 h-1) during cardiopulmonary bypass with induced hypothermia (25-26 degrees C) for 70-166 min. This rate of infusion during hypothermia was significantly slower (P less than 0.001) than that during normothermia. Thus, atracurium appeared to be suitable for use by continuous infusion in cardiac surgery and the temperature-dependent inactivation of atracurium was used to advantage because less drug was required during induced hypothermia.